Patent Application
20200227200
The present invention relates to a coil component, a circuit board, and a power supply device.
This application claims priority on Japanese Patent Application No. 2017-206159 filed on Oct. 25, 2017, the entire content of which is incorporated herein by reference.
One example of a circuit provided in a DC-DC converter for performing boost operation is a transformer-coupled boost chopper circuit of two-phase type shown in FIG. 5 of PATENT LITERATURE 1. PATENT LITERATURE 1 discloses a coil component used in this circuit and including a magnetic core obtained by combining two E-shaped cores. This magnetic core 300 includes, as shown in
PATENT LITERATURE 1: Japanese Laid-Open Patent Publication No. 2013-198211
A coil component of the present disclosure is a coil component used for two-phase transformer coupling, the coil component including: a first coil and a second coil; and a magnetic core at which the first coil and the second coil are provided. The magnetic core includes: a first magnetic leg at which the first coil is provided; a second magnetic leg at which the second coil is provided; a central leg portion interposed between the first magnetic leg and the second magnetic leg; a pair of connection portions connecting the first magnetic leg, the central leg portion, and the second magnetic leg in parallel; a main gap interposed in the central leg portion; a first gap interposed in the first magnetic leg; and a second gap interposed in the second magnetic leg. A coupling coefficient between the first coil and the second coil is not less than 0.7.
A circuit board of the present disclosure includes the coil component of the present disclosure.
A power supply device of the present disclosure includes the circuit board of the present disclosure.
For the coil components used in two-phase transformer coupling described above, it is desired that magnetic saturation is less likely to occur.
Circuit components such as switches are connected via a wiring pattern and the like to the first coil 101 and the second coil 102 described above. Due to manufacturing error in the wiring pattern and the circuit components, variation in connection conditions, or the like, a great difference can occur between currents flowing through the respective coils 101, 102. In the above magnetic core 300, there is a possibility that magnetic saturation is caused by the current difference. The reason will be described below. In
In the coil component 400 shown in I2) is to pass through the transformer coupling magnetic path, in addition to the above interlinkage magnetic flux. As is obvious from the above expression, as the current difference (I1
I2) between the coils 101, 102 increases, the amount of the magnetic flux to pass through the transformer coupling magnetic path increases, so that the magnetic core 300 reaches magnetic saturation. When magnetic saturation occurs, predetermined voltage transforming operation such as boost operation or step-down operation cannot be performed.
For example, by increasing the sectional area of a magnetic path of a magnetic core, magnetic saturation can be suppressed. However, in this case, the size of the coil component increases. Alternatively, for example, by detecting a current difference and separately providing a control circuit for reducing the current difference, magnetic saturation due to the current difference can be made less likely to occur. However, in this case, the circuit configuration is complicated. Therefore, it is preferable that the coil component has a small size and a simple configuration and is less likely to cause magnetic saturation.
Considering the above, one object is to provide a coil component in which magnetic saturation is less likely to occur. Another object is to provide a circuit board and a power supply device in which magnetic saturation is less likely to occur.
In the above coil component, magnetic saturation is less likely to occur. The above circuit board and the above power supply device enable predetermined voltage transforming operation to be favorably performed.
First, an embodiment of the present disclosure is listed and described.
(1) A coil component according to one mode of the present disclosure is a coil component used for two-phase transformer coupling, the coil component including: a first coil and a second coil; and a magnetic core at which the first coil and the second coil are provided. The magnetic core includes: a first magnetic leg at which the first coil is provided; a second magnetic leg at which the second coil is provided; a central leg portion interposed between the first magnetic leg and the second magnetic leg; a pair of connection portions connecting the first magnetic leg, the central leg portion, and the second magnetic leg in parallel; a main gap interposed in the central leg portion; a first gap interposed in the first magnetic leg; and a second gap interposed in the second magnetic leg. A coupling coefficient between the first coil and the second coil is not less than 0.7.
In the above coil component, in addition to the main gap, gaps are also provided to the magnetic legs at which the coils are provided. Therefore, in a case where there is substantially no difference between DC currents flowing through the respective coils, magnetic saturation due to excitation by the DC currents described above can be made less likely to occur, owing to the main gap. Further, even when a difference occurs between currents flowing through the respective coils, magnetic saturation due to the current difference can be made less likely to occur, owing to the gaps provided in the respective magnetic legs. Thus, the above coil component is less likely to cause magnetic saturation. In particular, the above coil component is less likely to cause magnetic saturation while having a simple structure in which gaps are provided in the respective magnetic legs.
In addition, in the above coil component, the gaps are provided in the respective magnetic legs within such a range that causes the coupling coefficient between both coils to be not less than 0.7. Therefore, increase in ripple current due to reduction of the coupling coefficient is small (see test example 1 described later), and thus the influence of ripple current on the entire circuit can be reduced. If the coil component as described above is used for a voltage transforming circuit such as a two-phase transformer-coupled boost/step-down circuit, magnetic saturation due to the above current difference is less likely to occur and increase in ripple current is small, and therefore predetermined voltage transforming operation can be favorably performed.
Further, the gaps provided in the respective magnetic legs can be made small (see the following configurations (2) and (3)), and thus it is not necessary to excessively increase the size of the magnetic core including the gaps. Accordingly, the above coil component has a small size.
(2) As an example, the above coil component may be configured such that each of a gap length of the first gap and a gap length of the second gap is shorter than a gap length of the main gap.
In the above configuration, since the gap lengths of the magnetic legs are shorter than that of the main gap, the coupling coefficient can be readily ensured to be great and increase in ripple current can be readily reduced. In addition, increase in the size of magnetic core including the gaps can be readily suppressed. Therefore, in the above configuration, magnetic saturation is less likely to occur, the influence of ripple current can be readily reduced, and size reduction can be achieved.
(3) As an example, the coil component of the above (2) may be configured such that each of the gap length of the first gap and the gap length of the second gap is not greater than 10% of the gap length of the main gap.
In the above configuration, the gap lengths of the magnetic legs are even shorter than that of the main gap. Therefore, in the above configuration, magnetic saturation is less likely to occur, the influence of ripple current can be more readily reduced, and further size reduction can be achieved.
(4) A circuit board according to one mode of the present disclosure includes the coil component according to any one of the above (1) to (3).
The above circuit board includes the above coil component in which magnetic saturation due to the current difference is less likely to occur and increase in ripple current is small. Therefore, if the above circuit board is used for a voltage transforming circuit such as a two-phase transformer-coupled boost/step-down circuit, predetermined voltage transforming operation can be favorably performed.
(5) A power supply device according to one mode of the present disclosure includes the circuit board according to the above (4).
The above power supply device includes the above circuit board provided with the above coil component in which magnetic saturation due to the current difference is less likely to occur and increase in ripple current is small. Therefore, if the above power supply device is used for a converter such as a two-phase transformer-coupled boost/step-down converter, predetermined voltage transforming operation can be favorably performed.
Hereinafter, the coil component, the circuit board, and the power supply device according to the embodiment will be specifically described, with reference to the drawings as necessary. In the drawings, the same reference characters denote the same elements.
With reference to
The coil component 4 of embodiment 1 is used for two-phase transformer coupling, and as shown in
Further, in the coil component 4 of embodiment 1, the magnetic core 3 has gaps (first gap 31g, second gap 32g) also in the respective magnetic legs 31, 32, in addition to the main gap 33g. In addition, in the coil component 4, the coupling coefficient between the first coil 1 and the second coil 2 is not less than 0.7. Hereinafter, each constituent member will be described.
The first coil 1 and the second coil 2 each include a cylindrical winding portion formed by winding a wire helically. A power supply 51 (
As the wires forming the coils 1, 2, coated wires obtained by forming insulating coats around the outer surfaces of conductor wires can be favorably used. Examples of the material forming the conductor wires include copper, aluminum, and an alloy thereof. The material forming the insulating coats is, for example, resin such as polyamide-imide called enamel. In this example, the wires forming the coils 1, 2 are coated rectangular wires having the same specifications (material, width, thickness, sectional area, and the like). In addition, the coils 1, 2 in this example are cylindrical edgewise coils having the same specifications (winding diameter, the number of winding turns, normal length, and the like).
The specifications of the wires and the specifications of the winding portions can be selected as appropriate. As another example of the wires, a known wire material used for coils, e.g., a rectangular wire, a round wire, a coated round wire, or a litz wire can be used. As in this example, using a rectangular wire as the conductor wire facilitates increase in the space factor and facilitates formation of a small-sized coil. In addition, the coil formed by using a rectangular wire as the conductor wire is more excellent in shape keeping property than a litz wire, and can retain the hollow shape even if the coil is manufactured independently of the magnetic core 3. Further, using a cylindrical edgewise coil as in this example facilitates manufacturing even in a case where the winding diameter is comparatively small, and thus provides excellent manufacturability.
The magnetic core 3 is a magnetic member including a soft magnetic material and forming a closed magnetic path. The magnetic core 3 includes the columnar first magnetic leg 31 at which the winding portion of the first coil 1 is provided, the columnar second magnetic leg 32 at which the winding portion of the second coil 2 is provided, the columnar central leg portion 33 interposed between both magnetic legs 31, 32 arranged side by side so as to be separated from each other, and the pair of plate-shaped connection portions 34 sandwiching the first magnetic leg 31, the central leg portion 33, and the second magnetic leg 32 arranged in this order, and connecting these. The magnetic core 3 included in the coil component 4 of embodiment 1 has the main gap 33g interposed in the central leg portion 33, the first gap 31g interposed in the first magnetic leg 31, and the second gap 32g interposed in the second magnetic leg 32. In this example, as shown in
The magnetic core 3 in this example is formed by combining a pair of E-shaped divided core pieces 3a, 3b such that their opening portions face each other, as shown in
In this example, the divided core pieces 3a, 3b have the same shape and the same size. Therefore, in the following description, one divided core piece 3a will be described as a representative. For the other divided core piece 3b, the following description can be applied by replacing reference character “a” with “b”. Forming both divided core pieces 3a, 3b in the same shape and the same size provides such effects that, for example, when the divided core pieces 3a, 3b are molded by a mold, they can be molded by the same mold, leading to excellent mass productivity, and they can be easily combined, leading to excellent assembly operability.
The divided core piece 3a includes two magnetic leg pieces 31a, 32a forming parts of the magnetic legs 31, 32, a central leg piece 33a interposed between the two magnetic leg pieces 31a, 32a and forming a part of the central leg portion 33, and one connection portion 34a supporting the two magnetic leg pieces 31a, 32a and the central leg piece 33a. The two magnetic leg pieces 31a, 32a and the central leg piece 33a protrude from the inner surface of the connection portion 34a. In this example, the protrusion heights of both magnetic leg pieces 31a, 32a are substantially equal to each other, and slightly greater than the protrusion height of the central leg piece 33a. Therefore, when both divided core pieces 3a, 3b are combined with each other such that predetermined spaces are formed between the magnetic leg pieces 31a, 31b and between the magnetic leg pieces 32a, 32b, a larger space than the above spaces between the magnetic leg pieces can be provided between the central leg pieces 33a, 33b of both divided core pieces 3a, 3b. This larger space is defined as the main gap 33g. The space between the two magnetic leg pieces 31a, 31b forming the first magnetic leg 31 is defined as the first gap 31g. The space between the two magnetic leg pieces 32a, 32b forming the second magnetic leg 32 is defined as the second gap 32g.
The magnetic legs 31, 32 (magnetic leg pieces 31a, 32a, 31b, 32b) and the central leg portion 33 (central leg pieces 33a, 33b) may have appropriate columnar shapes such as a cylindrical shape and a rectangular parallelepiped shape, for example. The magnetic legs 31, 32 may have shapes not similar to the inner circumference shapes of the coils 1, 2, but if they have shapes similar to the inner circumference shapes of the coils 1, 2 (in this example, have cylindrical shapes), the coils 1, 2 and the magnetic legs 31, 32 can be easily combined with each other, leading to excel lent manufacturability of the coil component 4. The connection portions 34 (34a, 34b) may have rectangular plate shapes, for example. The shape of the magnetic core 3 (shapes of the magnetic legs 31, 32, the central leg portion 33, and the connection portion 34) can be selected as appropriate within such a range as to obtain a predetermined magnetic path sectional area.
The coil component 4 has the main gap 33g in the central leg portion 33 at which both coils 1, 2 are not provided, in the magnetic core 3. In the magnetic core 3 as described above, in a case where the coil component 4 is used for two-phase transformer coupling, magnetic saturation due to a leakage magnetic flux based on each coil 1, 2 is less likely to occur. The coil component 4 also has the gaps 31g, 32g in the magnetic legs 31, 32 at which the coils 1, 2 are provided, in the magnetic core 3. In the magnetic core 3 as described above, in a case where the coil component 4 is used for two-phase transformer coupling and a difference occurs between currents flowing through both coils 1, 2, magnetic saturation due to a magnetic flux based on the current difference is less likely to occur.
The gap length L33 of the main gap 33g is set as appropriate so as to reduce magnetic saturation due to a leakage magnetic flux as described above. The gap length L31 of the first gap 31g and the gap length L32 of the second gap 32g are set within such a range as to reduce magnetic saturation due to the current difference as described above and prevent the coupling coefficient between both coils 1, 2 from being excessively reduced due to the gaps 31g, 32g. This is because reduction in the coupling coefficient leads to increase in ripple current. Increase in ripple current can lead to increase in loss of semiconductor elements used for switches 52 to 55 (
The gap lengths L31, L32 may be different from each other. However, if they are substantially equal to each other as in this example, it becomes easy to cause a magnetic flux to uniformly flow through the magnetic legs 31, 32.
Besides, the gaps 31g, 32g may be provided to the magnetic core 3 so as to be located in the respective coils 1, 2, as shown in
Since the coil component 4 of embodiment 1 is used for two-phase transformer coupling, the first coil 1 and the second coil 2 are mounted to the magnetic core 3 so as to mutually cancel magnetic fluxes generated by the respective coils 1, 2 during energization. In addition, currents are supplied to the coils 1, 2 so as to form such flow of magnetic fluxes.
In the coil component 4 of embodiment 1, although the magnetic core 3 has the gaps 31g, 32g in addition to the main gap 33g as described above, the coupling coefficient between both coils 1, 2 is not less than 0.7. Therefore, in a case of constructing, for example, a two-phase transformer-coupled voltage transforming circuit provided with the coil component 4, increase in ripple current is small and voltage transforming operation such as boost operation and step-down operation can be stably performed over a long period. As the coupling coefficient increases, increase in ripple current can be more readily reduced. From this standpoint, the coupling coefficient is preferably not less than 0.75 and further preferably not less than 0.78 or not less than 0.8. The gap lengths L31, L32 are set so that the coupling coefficient becomes not less than 0.7.
It is noted that the coupling coefficient is calculated from the following relational equation. Where the coupling coefficient is denoted by k, the self-inductance of the first coil 1 is denoted by L1, the self-inductance of the second coil 2 is denoted by L2, and the mutual inductance between both coils 1, 2 is denoted by M, the coupling coefficient k satisfies k2=M2/(L1BL2).
Using commercial simulation software or the like, correlation data between the coupling coefficient and ripple current, correlation data between the applied current value and the gap lengths L31, L32 for each coupling coefficient, and the like can be calculated in advance. By using the above correlation data, it is possible to easily select more preferable values of the coupling coefficient, the gap lengths L31, L32, the used current values, and the like in accordance with desired requirements.
As the magnetic core 3 (here, divided core pieces 3a, 3b), various types of cores made of known materials can be used. Examples thereof include a sintered body such as a ferrite core, a powder compacted body using powder of soft magnetic material, a molded body made of a complex material including resin and powder of soft magnetic material, and a stacked body formed by stacking soft magnetic sheet materials such as electromagnetic steel sheets.
At least one of the main gap 33g and the gaps 31g, 32g may be an air gap. For example, the coil component 4 may be provided with a shape retaining member (not shown) that can keep the combined state of the divided core pieces 3a, 3b such that the main gap 33g is an air gap and the gaps 31g, 32g partially include air gaps. At least one of the main gap 33g and the gaps 31g, 32g may include a gap material formed from a solid non-magnetic material. Examples of the non-magnetic material include a non-metal inorganic material such as alumina, and a non-metal organic material such as resin. As the gap material, various types such as a flat plate or a resin molded body having a predetermined shape may be used. The gap material may be fixed to the divided core pieces 3a, 3b by an adhesive agent or the like. One or two of the main gap 33g and the gaps 31g, 32g may be an air gap, and the others may include the gap materials. For example, the main gap 33g may be an air gap and the gaps 31g, 32g may include the gap materials. In this case, if the gap materials are materials having adhesion such as a double-sided tape or an adhesive agent, the gap materials can function as magnetic gaps and also as joining members for integrating the divided core pieces 3a, 3b. In a case where the magnetic leg pieces 31a, 31b and the magnetic leg pieces 32a, 32b of the divided core pieces 3a, 3b are joined to each other by the gap materials serving also as the joining members as described above, the strength of the assembled magnetic core 3 can be enhanced and the shape keeping property is improved. The thickness of a double-sided tape or an adhesive agent layer can be easily reduced, and therefore a double-sided tape or an adhesive agent layer can be favorably used for the gaps 31g, 32g that may be comparatively small magnetic gaps.
The coil component 4 of embodiment 1 can be used as one of components of the circuit board 5 for making two-phase transformer coupling. The circuit board 5 can be used as one of components of the power supply device 6 for making two-phase transformer coupling. In
The circuit board 5 of embodiment 1 includes the coil component 4 of embodiment 1, as shown in
The power supply device 6 of embodiment 1 includes the circuit board 5 of embodiment 1.
While the coil component 4 of embodiment 1 has a simple structure in which, besides the main gap 33g, the gaps 31g, 32g are also provided in the respective magnetic legs 31, 32 at which the coils 1, 2 are provided, even if there is a great difference between currents flowing through the respective coils 1, 2, magnetic saturation due to the current difference is less likely to occur. In addition, in the coil component 4 of embodiment 1, the gaps 31g, 32g are set within such a range that causes the coupling coefficient between both coils 1, 2 to be not less than 0.7. Thus, increase in ripple current can be reduced. This effect will be specifically described on the basis of the test examples below.
In a case where the circuit board 5 of embodiment 1 including the coil component 4 of embodiment 1 and the power supply device 6 of embodiment 1 including the circuit board 5 are used for, for example, a two-phase transformer-coupled boost/step-down circuit or a converter including this circuit, increase in ripple current is reduced and magnetic saturation based on the current difference described above is less likely to occur. Therefore, it is possible to favorably perform predetermined voltage transforming operation over a long period.
In addition, since the gaps 31g, 32g can be made comparatively small as described above, the magnetic core 3 including the gaps 31g, 32g can be readily downsized. Accordingly, the size of the coil component 4 of embodiment 1 is small.
Coil components to be used for two-phase transformer coupling were manufactured, and ripple current was investigated while the coupling coefficient was changed. A result thereof is shown in
Here, the coil component 400 shown in
Coil components to be used for two-phase transformer coupling were manufactured, the coil components including the one having only a main gap, and the one having both of a main gap and additional gaps. Then, the magnetic saturation state was investigated while the applied current value was changed.
Sample No. 1 is the coil component having both of the main gap and the additional gaps in the magnetic core, and corresponds to the coil component 4 of embodiment 1 shown in
Sample No. 100 is the coil component having only the main gap without having additional gaps, and corresponds to the coil component 400 shown in
The specifications of the coil components of both samples are substantially the same except for presence/absence of the additional gaps.
The gap lengths of the main gaps of both samples are 2 mm.
In sample No. 1, the gap lengths of the first gap and the second gap which are the additional gaps are 0.13 mm (6.5% of the main gap). The total gap length of the additional gaps is 0.26 mm, which is shorter than the gap length of the main gap.
The coupling coefficient of sample No. 1 is about 0.84. In sample No. 1, increase in ripple current as compared to a case where the coupling coefficient is 1 is about 1.2 times or less.
The coupling coefficient of sample No. 100 is about 0.98.
In this test, DC currents were varied and supplied to the first coil and the second coil. The current waveforms at this time were measured using a commercial current probe, and presence/absence of magnetic saturation was investigated. The average value of the DC currents supplied to the coils was selected in a range of 15 A to 100 A. Here, a current difference of about 5 A was provided between the first coil and the second coil. For example, in the condition that the average value of the DC currents is 80 A, the actual DC current flowing through the first coil is about 77.5 A, and the actual DC current flowing through the second coil is about 82.5 A. With respect to such a current difference, robustness is compared. For sample No. 1 and sample No. 100, the selected average value [A] of DC currents and the state of magnetic saturation are shown in Table 1 and Table 2.
For sample No. 1, ), and the vertical axis indicates the DC current value [A].
In this test, different measurement temperatures were used for sample No. 1 and sample No. 100. The measurement temperature for sample No. 1 including both of the main gap and the additional gaps was 130. The measurement temperature for sample No. 100 including only the main gap was 60
. It can be said that, as the measurement temperature increases, magnetic saturation is more likely to occur.
As shown in Table 1, it is found that the coil component of sample No. 1 having both of the main gap and the additional gaps is less likely to cause magnetic saturation even when a large current such as 100 A is supplied. In particular, it is found that even in the condition such as 130 in which magnetic saturation is likely to occur, the coil component of sample No. 1 is less likely to cause magnetic saturation. As shown in
As shown in Table 2, in the coil component of sample No. 100 having only the main gap, in spite of the condition in which the measurement temperature is low at 60 and magnetic saturation is less likely to occur, magnetic saturation occurs when the current value is 70 A. As shown in
From the above test, it has been shown that magnetic saturation can be reduced by providing gaps (additional gaps) to the respective magnetic legs at which the coils are provided, in addition to the main gap, in the coil component used for two-phase transformer coupling.
From the above test example 1 and test example 2, it has been shown that providing the additional gaps to the respective magnetic legs as described above within such a range that causes the coupling coefficient to be not less than 0.7 can reduce increase in the ripple current and can make magnetic saturation less likely to occur. If the coil component as described above is used for, for example, a circuit board including a voltage transforming circuit such as two-phase transformer-coupled boost/step-down circuit, or a power supply device including such a circuit board, increase in ripple current is reduced and magnetic saturation is less likely to occur, and therefore it is expected that predetermined voltage transforming operation such as boost operation or step-down operation can be favorably performed over a long period.
The present invention is not limited to the above examples, but is defined by the scope of claims and is intended to include meaning equivalent to the scope of claims and all modifications within the scope.
For example, at least one of the following modifications can be made.
(1) The shapes or the division number of the divided core pieces may be modified. For example, one divided core piece is formed in an I shape (rectangular parallelepiped shape), and the other divided core piece is formed in an E shape. In addition, the first magnetic leg and the second magnetic leg of the E-shaped core piece are made longer than the central leg portion in accordance with the gap lengths, and then the I-shaped core piece is combined therewith. Thus, a coil component in which the gap lengths L31, L32 are shorter than the gap length L33 of the main gap can be constructed.
(2) The size of the first gap 31g formed in the first magnetic leg 31 and the size of the second gap 32g formed in the second magnetic leg 32 may be made different from each other.
(3) An interposing member made of an insulating material may be provided between the magnetic core and each of the first coil and the second coil, an insulating coating material covering each coil may be provided, or an insulating coating material covering the magnetic core may be provided. Such a modification can enhance insulation property between each coil and the magnetic core.
(4) The circuit board or the power supply device may be configured to perform only boost operation or perform only step-down operation.
It is noted that the coil component used for two-phase transformer coupling is, in other words, a coupling inductor, for example, and can be expressed as follows.
A coupling inductor having a first coil (1) and a second coil (2) provided at a magnetic core (3) so as to form two-phase transformer coupling, wherein
the magnetic core (3) includes
a coupling coefficient between the first coil (1) and the second coil (2) is not less than 0.7.
1, 101 first coil
2, 102 second coil
3, 300 magnetic core
3
a,
3
b divided core piece
31, 310 first magnetic leg
32, 320 second magnetic leg
33, 330 central leg portion
34, 34a, 34b, 340 connection portion
31
g first gap
32
g second gap
33
g main gap
31
a,
32
a,
31
b,
32
b magnetic leg piece
33
a,
33
b central leg piece
330
g gap
4, 400 coil component
5 circuit board
50 board body
51 power supply
52, 53, 54, 55 switch
56 capacitor
57 load
6 power supply device
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-206159 | Oct 2017 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2018/031031 | 8/22/2018 | WO | 00 |
